Hypsirhina longicauda Bourret, 1934 Bulletin Générale de l’Instruction Publique,
1934:20. Syntypes MNHN 48.95, 48.96, 38.143. Type locality: Tonlé Sap,
Cambodia.
Enhydris longicauda - Smith, 1943 Fauna of British India…Reptilia and Amphibia
Vol. 3:386.
Enhydris innominata longicauda 1971 Saint
Girons, Société du Science Naturelles
Physiques du Maroc 51:221.
Etymology: The
name longicauda is undoubtedly
derived from the Greek or Latin long meaning
“length,” and the Latin cauda meaning
“tail”. This refers to the relatively long tail of this species.
Distribution: This
species is restricted to Cambodia’s Great Lake, Tonlé Sap and the immediate
surroundings. This extensive and dynamic wetland ecosystem is part of the
Mekong drainage basin.
Diagnosis: A
snake with 21 rows of scales at mid-body, 124 - 133 ventral scales, and a dorsolateral
pattern that is mostly black-purple with large, lateral, dark scalloped
blotches. It can be distinguished from other Indochinese species with 21 scale
rows at midbody by the following characteristics. In pattern and color it is
most similar to Enhydris jagorii and Enhydris innominata. However, both jagorii and innominata demonstrate sexual dimorphism of the subcaudal scales
and show less lateral compression of the tail. These two species also have
different ventral scale count ranges, jagorii
has 117 - 127, and innominata has 108
- 117. Enhydris chanardi has fewer
scale rows (20 - 22) around the neck compared to longicauda (23 - 25), fewer ventral scales (110 - 122), and a
distinctive pattern of lateral spots involving 2 - 4 scales on scale rows 4-6. Enhydris enhydris and Enhydris subtaeniata also have 21 scale
rows at midbody, but they have a dorsal pattern of longitudinal stripes. E. subtaeniata has lateral spots on
scale rows 4 - 6, and a ventral scale count range of 136 - 153, E. enhydris have more than 153 ventrals.
Both these species have striated scales, while longicauda, chanardi, jagorii, and innominata do not. See Table 11 for a comparison of the other
species in this group.
Size: Of
39 specimens measured the longest female had a total length of 803 mm and a
tail that was 163 mm. The longest male had a total length of 676 mm and a 173
mm tail. The tail of this species range from 23 - 35% of the SVL: 23 - 35% in
males and 25 - 35% in females. Thus, this species shows no sexual dimorphism in
tail length, an unusual condition for a homalopsid; this is also reflected in
subcaudal counts. The wide range in tail length may have resulted from damaged
tail tips that were undetected.
The
head is relatively short, distinct from neck, and slightly depressed. Its head
is much wider than the head of E. innominata. The eyes are dorsolateral
and their diameter is about two-thirds of the eye-nostril distance.
On
the head the rostral is pentagonal and about 2.3 - 2.5 times broad as it is
tall . The nasal scales are in contact and semi-divided
with the nasal cleft touching the first labial. The broad internasal may be
single or double and slightly penetrates the nasals, it has almost the same
area as a single nasal scale, and it contacts the loreal scales on each side of
the head . The two prefrontal scales contact the loreal and
the supraocular. They are irregular in shape. The rectangular frontal is
slightly shorter than the interorbital distance. The parietals are almost the
same length as the frontal. The single supraocular is rectangular. The single
loreal is contacted by upper labials 1 - 3. The preocular
is usually single, rarely divided. It is rectangular with the dorsal edge
narrower than the ventral edge. There are two postocular scales (rarely one or
three) the upper one is larger and taller than the bottom scale. The temporal
formula is 1 + 2. There is an enlarged scale where the third row of temporal
scales should start, and the scales below it are indistinguishable from dorsal
scales. The primary temporal is taller than broad, however, it is small, and
the secondary and tertiary temporal scales are barely distinguishable from the
occipital scales. Upper labials number eight (rarely nine); the largest is
usually six (rarely seven); the fourth usually enters the orbit, rarely the
fifth enters the orbit.
On
the chin lower labials number 9 - 12 (usually 10), the largest lower labial is
usually six, rarely seven. There are two pairs of enlarged chin shields; the
anterior pair is larger. The anterior pair contacts lower
labials 1 - 4. The second pair of chin shields is separated by a pair of
smaller scales. Gulars number 7-10.
On
the body the anterior dorsal scale rows number 23 - 26 rows, with 24 being the
most frequent count. Scale rows at midbody number 21. Scale rows at postbody
are reduced to 19 or 20. The scales become more ovate posteriorly and show no
ornamentation. The scales in the first row are larger than those in the second.
Dorsal scales on the tail are ovate, and they number 8 - 10 rows at the base of
the tail. Ventral scales number 124 - 136; males have 126 - 131 and females
have 124 - 136. They are relatively wide, 3 - 4 times the length of a nearby
dorsal scale. The ventral scales are rounded. The anal plate is divided and
almost the same length as a ventral or slightly longer.
On
the tail the subcaudal scales are divided and number 53 - 76, males have 52 - 75
and females have 53 - 76. Thus this species shows no sexual dimorphism a
character that will separate it from E.
jagorii (males have 53 - 68 subcaudal scales and females have 48 - 54) and E. innominata (males have 51 - 56
subcaudal scales, while females have 42 - 49). Thus, even though the subcaudal
scale ranges of these species overlap E.
longicauda lacks sexual dimorphism in this character; this character state
is also supported by data presented by Saint Girons (1972). The tail is more
compressed posteriorly than at the base, and the dorsal crest is sharply
defined, this is not the case in innominata
or jagorii. At the base of the
tail the width is 74% of the height based on an average of five specimens.
Color
and Pattern. The head is uniform gray or black with indistinct darker spots on
each head plate. Adults have three rows of dorsal spots that do not fuse as in innominata. Some upper and lower labials
have a central yellow spot. The venter is a uniform black, but some specimens
have scattered yellow spots. The dark ventral pigment intrudes on to dorsal
scale rows 1 - 5 or 1 - 6 to form a scalloped pattern. Yellow spots or
crossbars less than one scale row wide occur between the constricted areas of
dark pigment, these number 34 - 41 on the body. The venter is a uniform black
in some specimens. The chin is often yellow or contains a significant amount of
yellow pigment. There are 35 - 40 black bars or spots on the vertebral row of
dorsal scales and they involve 2 - 3 paravertebral rows.
Reproduction: One
specimen (FMNH 259280) contained 18 oviductal eggs, and interestingly one well
developed embryo (0.9g, 104mm long) that had apparently died and lodged in the
female from the previous litter. It was severely dehydrated and contained no
yolk. The female was collected on 28 June.